Swimming and wading pools, as well as certain spas, are equipped with powerful water circulation filtration systems. Such pools use one or more drains in the pump return line that generate high flow, high suction conditions at their inlets. It is now recognized that such drain conditions can pose considerable risks to pool users, particularly children. The drain conditions can entrap swimmers, resulting in numerous reported annual drownings as a result of an inability to break free of the extreme suction condition. Hair and apparel may also be entangled in the drain, resulting in traumatic and physically dangerous situations. Disembowelments have also been reported.
As a result of these repetitive accidents, many jurisdictions have enacted regulations to obviate the prime causal factors. To limit suction conditions in the event of blockage, plural drains have been proposed. To limit local suction conditions at a particular drain, anti-vortex covers and grated openings have been required. Maximum pump suction conditions have also been specified. During use, however, the covers and openings may become dislodged and the protective features are lost. Accordingly, even the currently proposed circulation conditions do not entirely overcome acute suction conditions at the drain inlet.
Most of such regulatory approaches have focused on new installations, or conditioned approval of alterations to the installations on retrofitting the drainage system for compliance. The economics of retrofit have limited the use of these approaches in existing pool installations where the governmental control is not applicable.